Different apparatuses are known for robot-supported, automated contact tasks such as, for example, the processing (machining) of surfaces (e.g., grinding, polishing, etc.) as well as the manipulation of workpieces or machine elements (stacking, palletizing, mounting, etc.). The grinding apparatus described in publication U.S. Pat. No. 5,299,389 can be named as an example. In the case of this apparatus, a rotating grinding disk is moved toward the surface to be ground by means of an industrial robot. The contact between the grinding disk and the surface is recognized by means of the load current of the motor driving the grinding disk, which provides a method which is too imprecise for many applications. In general, in the case of robot-supported automated systems where the robot contacts an object, the problem consists in recognizing the moment of contact and the closed-loop control of the contact force.
Even in the case of modern, force-regulated systems, when the tool which is mounted on the robot contacts the surface to be contacted a shock-like contact force occurs which may not be a problem in many cases, but in applications where precision is crucial or where very sensitive workpieces have to be processed or machined, it is extremely troublesome and undesirable. It is only possible to regulate the contact force once the robot has contacted the surface, and consequently in practical applications the mentioned shock-like contact force is a necessary evil which can certainly be reduced (for example by inserting a passively flexible element in the drive train) but cannot be eliminated. The passive flexibility of a spring, however, acts in an uncontrolled manner and can disturb the desired process.
Known force-regulated systems are frequently not able to react quickly enough in the case of very rapid (i.e. high-frequency) disturbances, such as, for example, jerks or impacts, as the regulated drive train has a certain inertia which results in a corresponding reaction time. In the case of rigid systems (such as, for example, standard industrial robots) even the smallest displacements, if effected too quickly, will result in a high increase in the force.
In view of the above, there is a general need for an active handling apparatus (effector) for a manipulator such as an industrial robot, wherein the handling apparatus should be designed for the purpose of contacting surfaces in a practically jolt-free manner and subsequently of jerk-free control of the contact force.